There are a variety of different ways of heating or cooling a building. Examples include radiators, convector heaters, night storage heaters, fan heaters, electric radiant bar fires, warm air systems and air-conditioning.
Of these alternatives, the most widely used are radiator systems and storage heaters. Both of these types of heating system rely on the creation of a circulation of air within the space to be heated to transfer the heat from a local hot point--the radiator or the storage heater--to the remainder of the room, including its fittings and its occupants. This circulation of air, which is referred to as convection, is generated by air rising in front of the radiator or storage heater as it is heated. The warmed air rises to the ceiling before descending on the side of the room space opposite the radiator or heater, and then returning across the floor of the room, to be reheated.
The disadvantages of such heating systems are well-known. The greatest accumulation of heat is at ceiling level, away from the occupants, and this is wasteful. The coolest air is at or near floor level and this causes uncomfortable draughts. In order to produce the required circulation of air, the radiators or heaters have to be hot (generally between 80.degree. and 85.degree. C.) otherwise their efficiency falls rapidly, and at this temperature the air becomes dry, causing stuffiness and drying out both the furniture and any paintings within the room as well as the fabric of the room itself. There is also the possibility that small children or elderly people who touch the radiators or heaters can suffer burns.
The advantages of such heating systems are that they are inexpensive to install, their technology is widely understood and the necessary components are readily available.
Early electric underfloor systems, which were designed to use off-peak electricity and which treated the floor as if it was an enormous storage heater, were uncomfortable because they heated the floor to too high a temperature in the morning but yet left it too cold in the late afternoon and early evening.
More recent warm-water underfloor systems, which serve to circulate heated water through pipes which are set into the floor, or which use electric cables in the floor, to gently warm the floor, are much more successful. They warm the floor to a temperature approximately 3.degree. to 4.degree. C. higher than the ambient temperature required for the room space above the floor, generally to a maximum of about 25.degree. C., so that the floor does not actually feel hot to the touch. Yet, at this temperature, the floor radiates a gentle overall warmth, with no draughts and with the highest temperatures at floor level and the lowest temperatures at ceiling level. Moreover, such systems maintain a higher relative humidity than radiator or convector heater systems, which is itself more sympathetic to the room space, its contents and its occupants.
Of more recent interest, due to the rapidly escalating cost of fuels and the increasing concern for energy conservation, is the fact that warm-water underfloor heating systems can be approximately 40 to 50% more energy efficient than radiator systems.
However, while such underfloor systems are accepted as being significantly more comfortable and more energy-efficient than alternative forms of heating, their single significant disadvantage hitherto has been that their initial installation cost has been higher than for an alternative radiator system. This factor alone has been sufficient to inhibit the much wider installation of warm-water underfloor systems, despite the running cost and energy savings which would be achieved.
Market pressures on architects, developers and builders continually demand that the cost of building construction and refurbishment is kept to a minimum, and there have been many changes in building methods in this pursuit.
One such change has led to the replacement of traditional floorboards in the construction of timber floors by mass-produced panels of particulate chip-board or fibre-board. While there are underfloor heating systems which can be fitted between the floor joists below such floor panels, and which work completely satisfactorily, they are expensive to install and consequently they are only fitted in buildings where comfort is specified as a specific and particular objective.
Another such change is the move away from solid floor constructions, in which a fine screed of 50 to 100 mm. thickness is put on top of a concrete raft or block and beam construction, towards a floor construction which includes a layer of high-density foam insulation placed directly on top of the concrete raft or the block and beam, with the insulation layer then being covered by a floating layer of particulate chipboard or fibreboard panels. The panels are produced as standard sizes, for example, 18 mm. or 22 mm. in thickness, 600 mm. in width and 2400 mm. in length. Reasons for this change include not only reduced cost but also improved sound insulation and the elimination of the "wet trades" associated with having to lay the screed.
Paradoxically, this move away from a solid, screeded floor construction method, into which known underfloor heating systems could be incorporated most efficiently, towards a type of floor construction into which it has hitherto been most difficult to incorporate underfloor heating, will potentially reduce still further the number of new underfloor heating installations and the energy savings which they would have made.
It is accordingly a specific object of the present invention to provide a method of installing an underfloor heating system which is less expensive than the installation of a convection heating system. A more general object of the invention is the provision of an improved method of installing a heating/cooling system. Thus, although it is envisaged that the majority of applications of the invention will be in relation to heating systems, the invention is equally applicable to cooling systems and to systems which can provide both heating and cooling functions.
A further object of the invention is thus the provision of an improved heating/cooling system.
It is known from European Patent Specification No. 0 006 683 (Neate) that underfloor heating systems can be made using small-diameter tubing (i.e. tubing having an internal diameter of between 5 mm. and 9 mm.) pre-fabricated on thermally conductive wire-mesh frameworks as modules, which can be interconnected within a heating/cooling system so that each is connected to a flow and return supply from a heater/cooler. Where such modules are installed in solid floor screeds, the screed can be as thin as 50 mm.
It is known from German Patent Specification No. 3217578 (Jung) that an arrangement of modular interconnected panels made, for example, from chipboard, can be used to provide a continuous serpentine channel into which large diameter piping (i.e. having an external diameter of say 15 to 22 mm.) can be laid. The serpentine channel is then covered over with a metal sheet (to aid heat distribution) and with a timber or other floor finish. This form of heating system can be installed either on timber joists or laid on top of a layer of insulation laid over a concrete structural base.
It is also known that, where a floor is formed from chipboard or fibreboard panels laid on top of a layer of insulation, which has itself been laid on a concrete structural base, a serpentine recess can be formed within the top surface of the insulation into which large diameter continuous piping (i.e. piping having an external diameter of say 15 to 22 mm.) can be laid before the chipboard or fibreboard panels are placed in position. Such an arrangement of continuous piping provides an underfloor heating system, but it is inefficient due to the poor thermal contact between the piping and the underside of the floor and due to the large amount of heat absorbed from the piping by the insulation itself.
In order to achieve the most effective heat transfer from the piping or tubing to the floor, an underfloor heating system as described above requires the piping or tubing to be surrounded with a cement-based pug or screed which is used as an inexpensive conductor. This would be used automatically when the piping or tubing is installed in the screed of a solid floor, but it is required even when systems are installed between the floor joists below a suspended timber floor. This is due to experience which has shown that air gaps around the piping or tubing can inhibit heat transfer and that timber strip floorboards and chipboard and fibreboard panels are not good conductors of heat. Without the pug, or some other form of heat transfer means such as a metal plate, it is difficult to achieve the required uniform distribution of heat through a timber floor, despite the fact that the heat has only to be conducted through the thickness of the board.
It is accordingly a further object of the present invention to provide a method of installing an underfloor heating system which can be carried out more cost-effectively than existing methods of providing underfloor heating.
It is also known from German Patent Specification No. 3717577 (Kurz) to provide a composite heating panel which includes an upper covering layer of wood to which a layer of copper wire netting is attached. The copper wire netting is bonded to a chipboard panel within which large diameter copper tubes are disposed. This panel is intended to act as a room heater but would be too expensive for incorporation in an underfloor heating/cooling system.
A still further object of the present invention is thus the provision of an improved form of panel for use as part of a heating/cooling system.